1. Field of the Invention
This invention relates to a watercraft having a hull supporting a plurality of watercraft propulsion devices for generating thrust, and more particularly relates to a watercraft in which information can be mutually transmitted between controllers of the respective watercraft propulsion devices.
2. Description of the Related Art
With reference to FIG. 7, a watercraft may include two outboard motors 2, 2 disposed at a stern of a hull I of the watercraft. Throttle valves 3, 3 of the respective outboard motors 2, 2 are connected to a remote control lever 5 through transmission mechanisms 4, 4 such as, for example, mechanical cables, links or the like. Each outboard motor 2, 2 has an engine side ECU 6 that controls an ignition timing, a fuel injection timing, a fuel injection amount and so forth in accordance with throttle valve opening (load) detection amounts sent from throttle valve opening sensors mounted to the throttle valves 3, 3 and engine speed detection amounts sent from respective crankshaft angle sensors (not shown).
In the outboard motors 2, 2, when an operator pivots the remote control lever 5 to vary the throttle valve openings, the respective engine side ECUs 6, 6 control the fuel injection amounts, the ignition timings, etc. in accordance with the openings of the respective throttle valves 3, 3 to adjust the engine speeds.
Meanwhile, the mechanical transmission mechanisms 4, 4 connecting the remote control lever 5 and the throttle valves 3, 3 of the respective outboard motors 2, 2 to each other may have production errors, adjustment errors, design changes and the like. Therefore, even though operational amounts of the remote control lever 21 are equal, the openings of the throttle valves 3, 3 can differ from each other. Consequently, the engine speeds of the respective outboard motors 2, 2 can be different from each other. As such, the thrusts of the respective outboard motors 2, 2 can be different from each other, thus urging the hull I to move in a direction that is not intended by the operator even though the motors are both steered in straight-ahead positions.
In Japanese Patent Document No. JP-A-Hei 8-200110, the respective engine side ECUs 6, 6 are connected to each other through a communication line 8 using connectors 7. Various detection amounts (i.e., operational information) such as, for example, the throttle valve openings and the engine speeds are mutually transmitted between the respective ECUs 6, 6 through the communication line 8. In addition, detection amounts of an atmospheric air temperature sensor and an atmospheric pressure sensor which are attached to one of the outboard motors 2, 2 can be sent to the other outboard motor 2.
As noted above, the engine side ECUs 6, 6 send and receive the engine speed signals of the respective outboard motors 2, 2 through the communication line 8. If a difference between the engine speeds of the respective engines is larger than a preset amount under a normal running condition, the engine side ECUs 6, 6 control the engine speeds of the respective outboard motors 2, 2 to keep the difference within an objective range.